Each person gets onevote, but can transfer it from 1st to 2nd to 3rd choice and so on. A voter needs to rank their preferred options 1,2,3 and so on.
Constituency
Each has multiple members rather than just one. In order to be elected the candidate needs to reach a number of votes which has been determined using the droop formula.
Quota
If a candidate reaches the quota, they are elected and the excess votes are redistributed. If no one reaches the quota the candidate with the least number of votes is eliminated and their 2ndpreference votes redistributed. The process continues until all the vacancies are filled.
Where
Northern Irish Assembly, as well as local elections in Wales, Scotland and NorthernIreland.